The present invention relates to a method for centering the wheels of a two wheel set with the centerline extending between dead centers of a machining-, measuring-, or testing-apparatus by means of a lifting arrangement.
The present invention relates further to an apparatus for carrying out the method.
Wheel set turning machines are for instance known by the DT-PS No. 1,270,361 or the DT-PS No. 1,477,587 in which a wheel set to be reprofiled is lifted off the rails and moved upwardly by a single device arranged centrally between the rails. A single centralizing arrangement, provided either adjacent the head stock or the tail stock of the wheel set turning machine, is used which shall assure that the lifting device, lifting the wheel set, positions the latter in such a manner that the centers of the two wheel coincide with the centerline of the machine extending between the dead centers of the head and tail stock, so that the dead centers of the wheel set turning machine may exactly engage into the conical center bores of the wheel set shaft to thus centralize the wheel set. After the wheel set has been received between the dead centers of the wheel set turning machine, entrainment means are engaged with the wheel set and the lifting device is again lowered. In practice it has however been shown that the positioning of wheel sets with the known devices cannot be carried out with the required exactness. With the known devices, the wheel sets to be reprofiled are positioned relative to the centerline of the machine too high, too low or inclined to the centerline. This will result in considerable damage of the conical center bores in the wheel set axle, whereby subsequent thereto remachining of these center bores will be necessary, and to a faulty gripping of the wheels of the wheel set. Such a faulty gripping of the wheel set will result that the wheels of the set will subsequently be reprofiled with a wrong distance between the wheels and a distorted profile.
An inclined position of the wheel set will result when asymmetrical loads act on the axle of the wheel set to be machined. Such asymmetrical loads may for instance result from drive motors or gearings connected to the axle of the wheel set. At such an asymmetrical load distribution, the central lifting device and the lateral arms thereof are likewise asymmetrically loaded, which results in a bending of the lifting cylinder and the arms thereof. A further cause of the inclined position of the wheel set is the difference between the diameters of the two wheels of the set which may be rather considerable at the tread surface as well as at the wheel flange. If perchance the wheel with the smaller diameter is located on the side of the wheel set on which the greater load acts, then these two features will be added to each other to contribute to the error producing an inclined position of the wheel set axis. If now the centralizing device is also located on the mentioned side of the wheel set turning machine, then the wheel set will be lifted by the lifting device controlled by the centralizing arrangement until the smaller diameter wheel located on the heaver side of the wheel set is exactly centrally positioned. In this position the lifting device is stopped. However, on the other side of the wheel set the conical center bore will be much too high, so that during movement of the dead centers into the center bores, contact along only a small surface will initially result at the higher side of the wheel set. The dead center of the wheel set turning machine moves now forceably into the conical center bore and produces thereby, due to its small surface contact, a deep groove in the latter and pushes the wheel set against the force of the lifting device downwardly, whereby the axis of the wheel set will be simultaneously elastically bent so that the wheel on this one side will assume an inclined position. The wheel is now received and held in this inclined position by the clamps on the face plate, so that this wheel will tumble during the reprofiling thereof.
A wheel set measuring apparatus is disclosed in the DT-PS No. 1,142,184 in which likewise the problem exists to position the wheel set as exactly as possible along the centerline of the apparatus, even though the wheels after the centralizing thereof are not engaged by entrainment means and fixed in their respective positions. The mentioned German patent suggests to lift each wheel of the wheel set to be positioned with a separate lifting device, whereby in order to assure a synchronous movement of the lifting devices the same amount of oil is simultaneously fed to the same. The pressure conduits of the lifting cylinders of the lifting devices are thereby connected with pressure accumulators. The elevation at which the wheel set has to be lifted is also in this construction determined solely by a single centralizing device which engages only one of the wheels of the set. Thereby differences of the diameters of the wheels of the set and an inclined position of the axis thereof will not be taken into account, so that centralizing errors will result. The two lifting devices have then the task, when the wheel set is brought into its central position, to relieve the dead centers from the wheel set weight. At an asymetrical load the lifting devices can likewise not accomplish the centralizing task, because at each lifting device a different pressure will result, due to the different weight of the portion of the wheel set resting thereon, so that the pressure accumulators connected to the pressure conduits will be filled in a different manner. Since however both lifting devices are supplied with the same oil volume, the higher loaded lifting device will necessarily start later. This will result under certain circumstances to a dangerous inclined position of the wheel set.
With the means known in the art it is therefore not possible to properly centralize the axis of a wheel set with the centerline of a machining-, measuring-, or testing-apparatus.